001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 * 019 */ 020 021package org.apache.directory.server.dns.io.encoder; 022 023 024/** 025 * 3. The DNAME Resource Record 026 * 027 * The DNAME RR has mnemonic DNAME and type code 39 (decimal). 028 * 029 * DNAME has the following format: 030 * 031 * <owner> <ttl> <class> DNAME <target> 032 * 033 * The format is not class-sensitive. All fields are required. The 034 * RDATA field <target> is a <domain-name> [DNSIS]. 035 * 036 * The DNAME RR causes type NS additional section processing. 037 * 038 * The effect of the DNAME record is the substitution of the record's 039 * <target> for its <owner> as a suffix of a domain name. A "no- 040 * descendants" limitation governs the use of DNAMEs in a zone file: 041 * 042 * If a DNAME RR is present at a node N, there may be other data at N 043 * (except a CNAME or another DNAME), but there MUST be no data at 044 * any descendant of N. This restriction applies only to records of 045 * the same class as the DNAME record. 046 * 047 * This rule assures predictable results when a DNAME record is cached 048 * by a server which is not authoritative for the record's zone. It 049 * MUST be enforced when authoritative zone data is loaded. Together 050 * with the rules for DNS zone authority [DNSCLR] it implies that DNAME 051 * and NS records can only coexist at the top of a zone which has only 052 * one node. 053 * 054 * The compression scheme of [DNSIS] MUST NOT be applied to the RDATA 055 * portion of a DNAME record unless the sending server has some way of 056 * knowing that the receiver understands the DNAME record format. 057 * Signalling such understanding is expected to be the subject of future 058 * DNS Extensions. 059 * 060 * Naming loops can be created with DNAME records or a combination of 061 * DNAME and CNAME records, just as they can with CNAME records alone. 062 * Resolvers, including resolvers embedded in DNS servers, MUST limit 063 * the resources they devote to any query. Implementors should note, 064 * however, that fairly lengthy chains of DNAME records may be valid. 065 * 066 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> 067 */ 068public class DnameRecordEncoder 069{ 070}